1. Field of the Invention
The present invention relates to an overheat prevention device for use in a projection apparatus.
2. Descriptions of the Related Art
All the ordinary projection apparatuses in the market comprise at least an illumination system and an imaging system. The illumination system is configured to supply homogeneous and concentrated beams to the imaging system, while the imaging system in turn is configured to output an image through the beams. In the illumination system, a high power bulb is typically used to form a light source module, which functions not only as the light source, but also as a main heat source in the projection apparatus (especially for a digital light processing (DLP) projection apparatus). For this reason, manufacturers of the projection apparatuses usually have to work out an effective solution to dissipate the heat generated by the light source module. For example, the heat can be dissipated with a fan or a heat pipe to reduce the operating temperature of the light source module and to prevent damage to both the light source module and the operation of the projection apparatus.
Since hot air rises, there is usually an uneven distribution inside the projection apparatus, so that temperatures at different area of the projection apparatus differ from each other. As a result, during the manufacturing of projection apparatuses, the manufacturers usually optimize the design of a heat dissipation mode based on the temperature distribution inside the projection apparatus that is placed on a flat surface. However, in practicality, rather than being placed on a flat surface, the projection apparatus is often suspended from a ceiling upside down, or is placed slantwise in response to an uneven operating environment.
Because the heat dissipation mode inside a projection apparatus is fixed at the time it was manufactured, when a projection apparatus operates in an inclined manner rather than being placed level on a flat surface, the temperature distribution therein will shift away from a desirable state. In other words, the heat dissipation structure, configured at the time of manufacturing, can not be changed to properly cool down the light source module which is the most prominent heat generating source. As a result, there is damage to the bulb inside the light source module which may lead to a premature end to the service life. More particularly, it will degrade the performance and even cause complete failure of the entire projection apparatus.
Therefore, to meet the expectations of consumers, manufacturers will need to provide an effective heat dissipating approach that will account for the temperature distribution variation inside the projection apparatus due to different placement orientations.